Sky View is a twin tower development with skybridge and skywalk observation deck located in Downtown Dubai, close walking distance from Burj Khalifa. The concept was initiated in 2008 but intense design work commenced only in late 2013, with site woks starting in early 2015. The building is scheduled to be handed over by end of 2019.
Photo 1. Sky View overlook
The towers are 61 and 57 floor in height,
reaching 264 meters. The skybridge is located
at floors 51-54, and the skywalk tourist
feature at floor 53-54. The development includes
5star hotel rooms (Address Hotel
brand), serviced hotel apartments, Skycollection
penthouse residential units, food
and beverage outlets, select retail space, tourist
attractions and rooftop bar with dedicated
elevator link.
Sky View is developed by Emaar. The design
architect was SOM from Chicago, the
lead consultant is Norr Group. Koltay Facades
provided façade engineering consultancy
and façade access strategy consultancy
from the early design stages to handover.
Structural engineering and MEP also
by Norr Group. The main contractor is ACC
– Arabian Construction Company, while the
façade package was shared in between Folcra
Beach and Al Ghurair Aluminium, with
a number of further specialist companies
and cladding subcontractors involved.
Image 1. Setting out comparison
Image 2. Wind Tunnel Test
Image 3. Inward opening door detail from Koltay Facades Design Intent drawings
The
tensioned glass walls were built by Novum
Structures. The tower glass is SS 20, supplied
by Guardian Glass, the stainless steel cladding
is 6WL from Rimex. The system profiles
are supplied by Technal, specifically developed
for this project. The BMU system is
supplied by Cox Gomyl.
As for each consultancy project, we started
with categorizing the façade systems for
easy reference. It is advisable to use similarities
for grouping in order to avoid too many
system types, and usually 4-8 systems should
cover a tower. For Sky View, while we
had only 7 system types and 2 balustrade
types for the towers, additional 11 façade
system types and 2 balustrade types
were used to describe the entire development
including the skywalk, the pavilions,
the podium.
Value engineering is often taken as a
simple cost reduction exercise executed
at the very end of the design stage of the
projects. This generally results into unpleasant
compromise on the building aesthetics,
with eliminated decorative features,
simplified geometry, substitute materials
and similar. It is utterly important that cost
efficiency items are considered throughout
the design process, to bring the resulting
tender design within budget.
Image 4. Patch fitted tensioned cable lobby glass wall detail
Image 5. BMU machine at level 50
Photo 2. Sky View overlook
Photo 3. Flying beam installation below the skybridge area
The first of many of those cost efficien-
cy improvements is an assessment of the
geometry and modulation. For Sky View,
the original architectural floorplan geometry
required 14 different extrusions, considering
that male-female unitized extrusions
can take up as much as 2.5 degrees angular
change. By altering the merging points of
arcs, slightly changing radiuses and amending
the modulation, the final solution looks
almost identical to the original outline,
but requires only 10 different mullion extrusions.
(Image 1- Setting out comparison)
An other important optimization exercise
to analyze the wind tunnel test results
and translate it to the most optimal framing
member sizes and glass thicknesses. While
for mullions a typical value could be selected
with local reinforcing or additional bracketing
at local high pressure spots, glass is
usually designed for the highest pressure,
to provide visual uniformity all over the
project. For Sky View however, the glazing
thickness was primarily driven by acoustic
requirements, and glass thicknesses optimized
for that.
The planar step of different
assembly types can be offset by varied air
gap size, adaptor profiles or special mullions.
At this stage of the design, the cladding
zones (distance from external side of
glass to edge of concrete slab) were finalized
and the required slab outline communicated
to the structural engineer.
The typical tower system is pressure equalized
male – female unitized system, with
solid stainless steel sheet infill elements and
glazing. The implemented system design
had high level of similarity to our tendered
design. The balcony doors are outward
opening side hinged doors, to enable facetation
as the building geometry requires.
The door frames are externally concealed
by flush glazing, the door hardware is drilled
through the glazing. However, some doors
are located at very narrow parts of the
uneven width balconies, and had to be inward
opening. This brought a challenge to
system design, where flush glazed concealed
frame, high level of watertightness and
inward operation was simultaneously required.
The implemented solution is less integrated
to the fixed frames as intended, but
still have relatively slim appearance.
The top few floors of each tower give
visual continuation of the towers above
the skybridge levels. However, the flo-
or plate outline changes and each floor
has a different geometry. Maintaining
the unitized system here is impractical,
as the new geometry would necessitate
additional extrusions to deal with tighter
radiuses.
Furthermore, the area is easily
accessible from the skybridge roof level,
via scaffolding. These top floors are more
like “pavilions in the sky”. These structures
were clad with stick system curtain walling,
while maintaining the visual match
to the tower areas below.
There are two main areas of the building
with patch fitted glass wall. The panoramic
elevator shaft is installed over architectural
steelwork, while the two elevations of
the ground level lobby are installed over a
one -way tensioned cable net. With those
cables spanning almost 20 meters, the reaction
forces on both sides are large. These
needed to be precalculated and coordinated
with the structural engineer to ensure
that they are accommodated by the interfacing
main structure.
The skywalk area is a giant steel truss itself,
with glazing on all sides. The perimeters
of the floor area are solid filled, just to
cater for a wider audience – some may feel
discomfort with fully glazed floor area. The
floor glazing has high level of redundancy,
consisting of 5 layers of glass laminated
with SGP in an IGU assembly. The double
glazing improves thermal performance
and reduces cooling loads, as well as
ensures clear view with no condensation
even on those days when the outside air
temperature drops below dew point and
humidity is high.
The skybridge itself has a 3 story tall trusswork
primary structure that was assembled
on ground and elevated in position by hydraulic
jacks. The main, 80 meters long portion
of the bridge was a single 165 tonnes
lifting operation over about a week time.
The bridge will house residential units and
have an infinity pool on top. The bottom
side of the bridge is clad with solid stainless
steel sheets.
During a late design review, just after procurement
of the façade package had started,
further decorative flying beam features
were added to the building. These give the
appearance of certain spandrel zones departing
from the tower to smooth the visual
transition towards the skybridge and skywalk.
While architecturally well placed, the
late change introduced complexity on the
façade access strategy, by blocking access
of the intended BMU machines to the areas
below the fly beam features.
This necessitated
modification of the strategy and further
BMU units and accessories. The dense bridge
truss limited the overall sizes of the BMU
machines placed at level 50, below the bridge
belly.
The machine and its counterweight
could not increase further, however the added
extendable pentograph cradle that was
needed to reach below the fly beam features
necessitated further measures of stabilizing.
The machine track was then brought
closer to the facades to reduce reach, by rearranging
the layout.
An other interesting area for cleaning
and maintenance access is the skywalk.
The bottom side is reached by monorail
system. The sides have an 800 mm external
walkway with upper rail for safety and for
spare glass manipulation. The roof glass is
walkable for cleaning. For reglazing, a small
custom built sliding gantry is provided that
needs to be assembled and after use disassembled
and stored away.
This gives a brief introduction to Sky
View’s façade package design and procurement
process. The building will soon be
ready to welcome visitors as a highlight of
Dubai Downtown.
Agnes Koltay, Koltay Facades
The article was based on a lecture
presented at the GLASS PERFORMANCE
DAYS 2019 Conference, which took place
on June 26-28, 2019. Tampere, Finland
